1. Field of the Invention
The present invention relates to an industrial welding robot and more particularly to a spot welding robot. More specifically, the present invention pertains to an industrial spot welding robot having conduits for supplying cooling medium and/or welding gun actuating fluid to the welding gun.
2. Description of the Prior Art
The spot welding is a typical resistance welding technique and comprises steps of superposing two or more metal sheets, placing the superposed metal sheets between a pair of electrodes and applying a depressing force through the electrodes to the superposed metal sheets while applying electric current through the electrodes so that welded spots are formed in the metal sheets. In this welding process, the electrodes are applied not only with an electric current but also with a depressing pressure so that the electrodes are subjected to a temperature rise. In order to suppress the temperature rise, the electrodes are generally made of a copper alloy having a superior thermal conductivity and facilities are provided for effecting liquid cooling of the electrodes.
Conventionally, a spot welding robot which is currently adopted in a car manufacturing factory has a spot welding gun of a so-called C-type or X-type which includes a pair of electrodes or a spot welding gun of a type having a backing electrode and a stud gun. The welding gun is generally mounted on a hand of a robot which is actuated by a control unit in accordance with a mode of operation which is in advance taught to the robot. In a modern welding robot, weldings can be made rapidly even at positions which would be difficult to have an access by a human hand and with a high accuracy in accordance with a schedule which is preliminarily taught to the robot. Thus, a welding robot is now regarded as essential for mass production in a manufacturing factory.
In a conventional welding robot, the conduits for supplying the cooling medium and the gun actuating working fluid are supported on a post provided for the purpose at a side of the robot body and connected with appropriate portions in the robot hand. In an alternative arrangement, the conduits for the cooling medium and the gun actuating working fluid are supported on the ceiling of the factory building. In order that the movements of the robot are not disturbed by the conduits, the conduits must be slackened at portions between the robot hand and the supporting post or the ceiling.
In the conventional arrangements, it has therefore been required to conduct adjustments of the lengths of the conduits after the installation of the robots. More specifically, the robot body is at first installed in a predetermined position and then the conduits are attached to desired portions with appropriate adjustments of the conduit lengths for providing required slackenings of the conduits. Thus, the installation of the conduits requires a lot of time and labor.
It should further be pointed out that, in the conventional robots requiring conduit supporting posts which are to be located in the vicinity of the robot bodies, there must be provided increased spaces for arranging the robots. A further disadvantage in the conventional structure is that the conduits for the cooling medium and the gun actuating working fluid are arranged in a relatively unstable way by being hung on the supporting posts or on the ceiling. The conduits arranged in this manner are frequently brought into contact with the robot body and the supporting posts during operations of the robot. Further, the conduits are repeatedly stretched and bent upon movements of the robot arm. Thus, the conduits are used in conditions in which they are very easily damaged. Still further, the conventional robot is disadvantageous in that the movements of the robot are restricted by the conduits.